1. Field of the present invention
The present invention relates to a brake system for a vehicle including a body frame that leans, two front wheels, and one rear wheel and a vehicle including the brake system.
2. Description of the Related Art
A vehicle is known which includes a body frame which leans in a left-and-right direction of the vehicle when the vehicle is cornering, two front wheels aligned side by side in a left-and-right direction of the body frame, and a central rear wheel which is disposed centrally between the two front wheels when the vehicle is seen from the front thereof with the body frame being in an upright state (for example, refer to International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio). A vehicle is also known which includes a body frame which leans in a left-and-right direction of the vehicle when the vehicle is cornering, two front wheels aligned side by side in a left-and-right direction of the body frame, and two rear wheels (for example, refer to Japanese Patent Unexamined Publication JPA-2011-195099).
The vehicles described in International Patent Publication No. 2012/007819, Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio and Japanese Patent Unexamined Publication JP-A-2011-195099 are vehicles which include a body frame which leans and two front wheels. The vehicle including the body frame which leans and the two front wheels includes a link mechanism. The link mechanism includes an upper cross member and a lower cross member. The link mechanism also includes a right side rod which supports right end portions of the upper cross member and the lower cross member and a left side rod which supports left end portions of the upper cross member and the lower cross member.
A middle portion of the upper cross member is connected to the body frame via a middle upper bearing so as to turn about a middle upper axis which extends in a front-and-rear direction of the body frame. The middle upper axis is inclined in such a way as to extend forwards in the front-and-rear direction of the body frame and upwards in an up-and-down direction of the body frame. The right end portion of the upper cross member is connected to the right side rod via a right upper bearing so as to turn about a right upper axis which extends in the front-and-rear direction of the body frame. The left end portion of the upper cross member is connected to the left side rod via a left upper bearing so as to turn about a left upper axis which extends in the front-and-rear direction of the body frame. A middle portion of the lower cross member is connected to the body frame via a middle lower bearing so as to turn about a middle lower axis which extends in the front-and-rear direction of the body frame. As with the middle upper axis, the middle lower axis is also inclined in such a way as to extend forwards in the front-and-rear direction of the body frame and upwards in the up-and-down direction of the body frame. The right end portion of the lower cross member is connected to the right side rod via a right lower bearing so as to turn about a right lower axis which extends in the front-and-rear direction of the body frame. The left end portion of the lower cross member is connected to the left side rod via a left lower bearing so as to turn about a left lower axis which extends in the front-and-rear direction of the body frame.
When the body frame leans in the left-and-right direction of the vehicle from its upright state, the upper cross member and the lower cross member turn relative to the body frame about the middle upper axis and the middle lower axis, respectively, so that a relative position of the two front wheels in relation to the up-and-down direction of the body frame changes. In addition, the middle upper axis and the middle lower axis are inclined in such a way as to extend forwards in the front-and-rear direction of the body frame and upwards in the up-and-down direction of the body frame, and therefore, the two front wheels move farther rearwards as they move upwards, while the two front wheels are displaced farther forwards as they move downwards. With the body frame being in the upright state, the upper cross member and the lower cross member are above the two front wheels in the up-and-down direction of the body frame. The link mechanism is above the left front wheel and the right front wheel in the up-and-down direction of the body frame when the vehicle is viewed from the front thereof with the body frame being in an upright state.
The vehicle including the body frame which leans and the two front wheels includes a right shock absorbing device which supports the right front wheel so as to move in the up-and-down direction of the body frame and a left shock absorbing device which supports the left front wheel so as to move in the up-and-down direction of the body frame. The right shock absorbing device is supported by the right side rod so that the right shock absorbing device is able to turn about a right axis which extends in the up-and-down direction of the body frame. The left shock absorbing device is supported by the left side rod so that the left shock absorbing device is able to turn about a left axis which extends in the up-and-down direction of the body frame. The vehicle described in International Patent Publication No. 2012/007819 includes further a handlebar, a steering shaft and a turn transmission. The handlebar is fixed to the steering shaft. The steering shaft is supported so as to turn relative to the body frame. When the handlebar is turned, the steering shaft also turns. The turn transmission transmits a turning motion of the steering shaft to the right shock absorbing device and the left shock absorbing device.
The vehicle including the body frame which leans and the two front wheels includes many on-board components provided on the periphery of the steering shaft. The on-board components include a lamp such as a headlamp, a radiator, a reservoir tank, an electric component such as a horn, a main switch of the vehicle, a stowage box, a stowage pocket and the like.
The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio include a left and right front wheel braking input member which controls a braking force generated on the right front wheel and the left front wheel. Additionally, the vehicle includes a rear wheel braking input member which controls a braking force generated in the central rear wheel. Further, the vehicle includes left and right front wheel and central rear wheel braking input member which controls braking forces generated in the central rear wheel and the right front and left front wheels.
A front wheel master cylinder is activated when the left and right front wheels braking input member is operated. A hydraulic pressure generated by the front wheel master cylinder activates a primary tandem master cylinder. A hydraulic pressure generated in the primary tandem master cylinder is divided evenly to be transmitted to a right brake provided on the right front wheel and a left brake provided on the left front wheel. The right brake and the left brake which have received the hydraulic pressures generate braking forces.
A rear wheel master cylinder is activated when the rear wheel braking input member is operated. A hydraulic pressure generated by the rear wheel master cylinder activates a secondary master cylinder. A hydraulic pressure generated by the secondary master cylinder is transmitted to a central rear brake provided on the central rear wheel. The central rear brake which has received the hydraulic pressure generates braking forces.
A front and rear wheel master cylinder is activated when the left and right front wheels and rear wheel input member is operated. A hydraulic pressure generated by the front and rear wheels master cylinder activates the secondary master cylinder. A hydraulic pressure generated by the secondary master cylinder is transmitted to a central rear brake provided on the central rear wheel. Additionally, a portion of the hydraulic pressure generated by the front and rear wheel master cylinder passes through the secondary master cylinder to activate the primary tandem master cylinder. A hydraulic pressure generated by the primary tandem master cylinder is divided evenly to be transmitted to the right brake provided on the right front wheel and the left brake provided on the left front wheel. The central rear brake, the right brake, and the left brake which have received the hydraulic pressures generate braking forces.
The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio use the three types of brake systems which are different in operation.
The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio which include the body frame which leans, the two front wheels, and the single rear wheel include the right front wheel, the central rear wheel, and the left front wheel which are aligned side by side in the left-and-right direction of the body frame when the vehicle is viewed from the front thereof with the body frame being in an upright state. Because of this, when the vehicle runs, the right front wheel, the central rear wheel, and the left front wheel basically pass over different road surfaces. The vehicle described in Japanese Patent Unexamined Publication JPA-2011-195099 which includes the body frame which leans, the two front wheels, and the two rear wheels include the right front wheel, the right rear wheel, the left front wheel, and the left rear wheel which are aligned side by side in the left-and-right direction of the body frame when the vehicle is viewed from the front thereof with the body frame being in an upright state. Because of this, when the vehicle runs, the right front wheel and the right rear wheel pass over road surfaces which are almost the same, and the left front wheel and the left rear wheel pass over road surfaces which are almost the same. In this way, the road surfaces which the wheels of the vehicle pass over which includes the body frame which leans, the two front wheels, and the single central rear wheel are different from the road surfaces which the wheels of the vehicle which includes the body frame which leans, the two front wheels, and the two rear wheels.
The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio which include the body frame which leans, the two front wheels, and the single rear wheel include the two front wheels, the two shock absorbing devices which support individually the two front wheels, the link mechanism which supports the two shock absorbing devices, the single central rear wheel, and one shock absorbing device which supports the single central rear wheel. The vehicle described in Japanese Patent Unexamined Publication JP-A-2011-195099 which includes the body frame which leans, the two front wheels, and the two rear wheels include the two front wheels, two shock absorbing devices which support individually the two front wheels, a link mechanism which supports the two shock absorbing devices, the two rear wheels, and one shock absorbing device which supports the two rear wheels.
There is a tendency that a ratio of the magnitude of load applied to the front wheels to the magnitude of load applied to the front wheels and the rear wheel or wheels becomes larger relative to that in the vehicle including the body frame which leans, the two front wheels, and the single central rear wheel than in the vehicle including the body frame which leans, the two front wheels, and the two rear wheels. It is noted that the load applied to the front wheels is not necessarily larger than the load applied to the rear wheel or wheels. In fact, the loads applied individually to the front wheels and the rear wheel or wheels change depending upon the layout of the drive source such as the engine mounted on the body frame, the seated position of the rider or the like.
The vehicles described in International Patent Publication No. 2012/007819, Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio and Japanese Patent Unexamined Publication JP-A-2011-195099 which include the body frame which leans and the two front wheels turn with the body frame leaning in the left-and-right direction of the vehicle. As this occurs, the vehicle including the body frame which leans and the two front wheels has a tendency that a load applied to the front wheel which defines the inner wheel having a smaller turning radius becomes relatively larger than a load applied to the front wheel which defines the outer wheel having a larger turning radius. This is attributed to the configuration of the vehicle in which the middle upper axis and the middle lower axis are provided so as to lean in such a way as to extend forwards in the front-and-rear direction of the body frame and upwards in the up-and-down direction of the body frame. With the body frame leaning in the left-and-right direction of the vehicle, the inner wheel is positioned upwards and the outer wheel is positioned downwards in the up-and-down direction of the body frame. In addition, the inner wheel is positioned rearwards in the front-and-rear direction and the outer wheel is positioned forwards in the front-and-rear direction of the body frame. A distance between the front wheel which defines the inner wheel and the rear wheel is shorter than a distance between the front wheel which defines the outer wheel and the rear wheel. Due to this, the vehicle including the body frame which leans and the two front wheels has the tendency that the load applied to the front wheel which defines the inner wheel having the smaller turning radius becomes relatively larger than the load applied to the front wheel which defines the outer wheel having the larger turning radius.
The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio which include the body frame which leans, the two front wheels, and the single rear wheel include the link mechanism which is provided above the right front wheel and the left front wheel in the up-and-down direction of the body frame when the vehicle is viewed from the front with the body frame being in an upright state. In this configuration, with the body frame being in the upright state, the right front wheel, the right shock absorbing device, the left shock absorbing device, and the left front wheel are aligned side by side in the left-and-right direction of the body frame, and the link mechanism is not present between the right front wheel and the left front wheel. Because of this, the distance between the right front wheel and the left front wheel of the vehicle described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio which include the body frame which leans, the two front wheels, and the single rear wheel is shorter than a distance between a right front wheel and a left front wheel of a vehicle in which a link mechanism is disposed between the right front wheel and the left front wheel. This causes a tendency that a difference between a load applied to the front wheel which defines an outer wheel having a larger turning radius and a load applied to the front wheel which defines an inner wheel having a smaller turning radius becomes smaller in the vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio which include the body frame which leans, the two front wheels, and the single rear wheel than that in the vehicle in which the link mechanism is disposed between the right front wheel and the left front wheel.
The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio have the configuration and characteristics which are described above. The vehicles described in International Patent Publication No. 2012/007819 and Catalogo partidi ricambio, MP3 300 LT Mod. ZAPM64102, Piaggio use the three types of brake systems which are different in operation.